Optimum health, functioning and nutritional status are key to the quality of life in the older American. More than 35 million Americans are over the age of 60, and the oldest old represent the fastest growing segment of the American population. Older persons are more frequent consumers of health care services and, when health fails, of long-term care facilities. The costs of these services are considerable. Impairment of taste and olfactory function can negatively impact dietary selection, nutritional status, morbidity and mortality in older persons (Schiffman,1997). While frailty and weight loss in the elderly are poor prognostic factors for debility and mortality, epidemic increase in middle-aged obesity with associated risk for cardiovascular disease, diabetes, dementia and "metabolic syndrome" is creating an enormous public health burden with grave implications for the next generation of older adults (Poirier et al., 2006). The middle aged obese have a higher risk of nursing home admission in late life and reducing obesity rates may thus reduce the later societal burden of nursing home care (Elkins et al., 2006). Clear elucidation of age-related changes in brain response to appetitive stimuli, during hunger and satiety, may suggest interventions to modulate food intake, obesity in middle aged and frailty in older adults. Similar to obesity, Alzheimer's disease (AD) is a pathologic process for which risk exists in middle age and severe consequences emerge in old age. Bio-behavioral markers in non-demented older adults at genetic risk for AD because of the APOE e4 allele have potential clinical significance for signaling disease in the pre- clinical period. AD patients show early and dramatic loss of memory, and particularly odor memory, and they demonstrate profound olfactory dysfunction in old age (Murphy, et al., 1990). Chemosensory, behavioral, and metabolic abnormalities lead to malnutrition and weight loss, furthering morbidity in this precarious disease population (Guirin et al, 2005;reviewed in Reynish et al., 2001). Despite the importance of clarifying the impact of central processes on nutritional aberrations in the age-related progression of both obesity and Alzheimer's disease processes, in neither population has chemosensory function and brain processing been directly addressed in a middle-aged cohort. Neuroimaging is the only method capable of revealing precise spatial information about age-related differences in cortical response to chemosensory stimuli in living humans. The present study will use the power of fMRI to image the aging brain while it is processing taste and odor information in order to test the overarching hypothesis that functional changes in central nervous system activity, detectable in the cortical representation on fMRI, constitute a major neural substrate for altered chemosensory function and preference in normal aging and AD. A better understanding of chemosensory function and preference may suggest avenues to optimize health and qualify of life in aging Americans. PUBLIC HEALTH RELEVANCE: Middle aged obesity has become an epidemic with serious public health consequences and the "metabolic syndrome," a cluster of closely related disease states that doubles risk of cardiovascular disease, triples risk of diabetes, and impacts cognitive function, affects one in four adults in most developed countries (Poirier et al., 2006). Obesity is responsible for increased per capita health care spending of approximately 50%, with costs rising by age and degree of obesity, and because midlife obesity is associated with increased chronic illnesses, future dementia, hospitalizations, and nursing home admission in old age, reducing obesity rates may thus reduce the later societal burden of long-term nursing home care (Elkins et al., 2006;Whitmer et al., 2005). Elucidation of age-related changes in brain response to appetitive chemosensory stimuli may suggest avenues to modulate food intake and obesity in middle age, and metabolic disease and cognitive impairment in older adults.